Tim Naish, of the New Zealand Institute of Geological and Nuclear Sciences, warns that Antarctic?s huge ice shelves may break up completely as the global climate warms. The recent collapse of the Larsen B Ice Shelf in Antarctica was ?a wakeup call to expect more collapses,? he says and believes that such collapses have ?a dramatic effect on global climate? by disrupting ocean currents.
Larsen B, made up of about 720 billion tons of ice, disintegrated after 50 years of sharp temperature rises on the Antarctic Peninsula. Ted Scambos, of the National Snow and Ice Data Center at the University of Colorado, who is one of three American researchers monitoring the Larsen ice shelf by satellite, says other ice shelves are also closer to the breaking point than previously thought. The ice shelves form when ice sheets spread off the land mass.
If average global temperatures continue to rise this century, as climate models currently predict, Naish believes the bigger Antarctic ice shelves, including several in the Weddell Sea, could become vulnerable. Scientists still know too little about the behavior of Antarctic ice sheets to predict whether these ice shelves will remain intact for decades or centuries.
Next year, a six-nation science team will drill into the seabed of the Ross Sea ice shelf as part of a study to understand the behavior of the region?s ice shelves during climatic change. The project will include the deepest core drilling yet attempted in Antarctica.
Naish says the Larsen?s collapse is a warning about the stability of Antarctica?s largest ice shelf, the Ross Ice Shelf, which at 332,000 square miles covers an area the size of France. ?It is becoming especially vulnerable as huge ice streams that feed it from West Antarctica begin to slow or have stopped,? Naish says. Even a partial collapse of the Ross Ice Shelf would be globally significant, as it would ?dramatically affect ocean circulation and climate.?
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While huge chunks of Antarctica are breaking off at the bottom of the Earth, at the top of the world the Arctic ice is thinning. Scientists now believe they have identified the mechanism which can explain why Arctic sea ice is getting thinner. In the summer, this thinning reaches more than 40% in some areas.
There are 2 causes: Rising air temperatures, due to global warming, are melting the ice from above, and warmer water is also rising from the depths of the ocean to attack the ice from below.
Professor Peter Wadhams, of the Scott Polar Research Institute in England, says that in 2000 he established the degree of thinning using measurements from submarines in 1976 and 1996. These measurements showed that a large area of the sea ice, stretching from the North Pole to the Fram Strait between Svalbard and Greenland, had thinned by 43% during the Arctic summers. U.S. data from the other side of the Arctic, between the Pole and the Bering Strait, found a similar thinning over the same period.
This degree of melting has been questioned by scientists who say the ice may not be missing, but simply concentrated in areas where it has not been found. But Wadhams says he has detected thinning that ranges from 16 feet 20 years ago to 9 feet today.?People say global warming can?t be raising air temperatures enough to melt the ice, because the Arctic winter temperature is around ?22 F anyway, and a one-degree warming would be irrelevant. But it?s the summer temperatures that matter. Arctic summers are getting longer, so there is longer for the warmer air to melt the snow and affect the ice beneath.
?The other mechanism is the warming of one or two degrees in the water under the ice -- enough to increase the bottom melting quite considerably. There is a cold water layer immediately beneath the ice. But that?s changing its stability and salinity, because of changes in the distribution of Siberian river water in the Arctic. Over a large area that cold water is becoming more saline and denser, which means it?s letting more heat rise through it.?
Wadhams thinks the Arctic could be ice-free during the summer by 2080. He says, ?The north-east passage across the top of Siberia is already close to becoming commercially viable. It will shorten the existing route from Europe to the Far East by about 40%, from 11,000 nautical miles to 7,000 nm. Containers going from Germany to Japan on Russian vessels are now using that route experimentally. There?ll be huge savings for shipping. And as the route lies through Russia?s territorial waters, it will collect fees for providing ice breakers, search and rescue services and so on.?
But wildlife experts aren?t happy about the change. Polar bears will face problems as the sea ice retreats and makes it harder for them to hunt seals. Scientists from Norway have begun a program to tag and monitor bears which, they say, are under threat from both climate change and pollution.
They also think man-made chemicals are entering the animals? food chain. Andrew Derocher of the Norwegian Polar Institute says the Arctic was being increasingly polluted by industrial chemicals that are carried northwards by ocean currents and winds. Because the chemicals bond well with fat, high levels build up in the seals? blubber. Studies show that the bears? fertility is being affected by the chemicals.
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Scientists will meet next week to discuss whether the recent melting of the Larsen B Antarctic ice shelf is evidence of global warming that will eventually cause oceans to flood coastal lands.
?The ice shelves are breaking up. The question we?re trying to answer is whether these ice shelves have gone through a periodic history of retreat and regrowth,? says Eugene Domack, a marine geologist at Hamilton College, where the two-day National Science Foundation Conference will begin April 4. At least 50 scientists representing 10 nations will attend the conference in upstate New York.
The Larsen B disintegration will not directly will not add to sea levels, but it could allow some land-based glaciers to move into the oceans and begin melting, which would raise sea levels significantly. Domack took part in the last scientific expedition to the ice shelf before it fractured and disintegrated during a 35-day period that ended March 7. During the January trip, Domack?s team confirmed that the formation had been undisturbed since the last ice age.
The research team suspects the buildup of greenhouse gas emissions in the atmosphere for the ice shelf's breakup. Some scientists warn that rising temperatures could melt the polar ice caps, contributing to a rise in sea levels and cause flooding around the world?s coasts.
The Antarctic ice shelf has been under observation since 1995 when its northernmost section collapsed in a similarly dramatic event. About 60 percent ? roughly 3,420 square miles ? of the Larsen Shelf has disappeared over the last five years.
To learn what effect the deteriorating north and south poles will have in the future, read ?The Coming Global Superstorm? by Whitley Strieber and Art Bell, now only $9.95 for an autographed hardcover,click here.
To see amazing images of the Antarctic ice shelf break-up,click here.
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